In conventional, there has been known a throttle control apparatus which is provided with an accelerator opening degree sensor detecting an accelerator opening degree, so that electrically controls an opening degree of a throttle valve on the basis of an output signal of the accelerator opening degree sensor in correspondence to a pedaling amount of an accelerator pedal. (This structure is disclosed in Japanese Unexamined Patent Publication No. 10-287147).
Further, a structure disclosed in Japanese Unexamined Patent Publication No. 2001-180326 is generally used as the accelerator opening degree detecting apparatus in the throttle control apparatus mentioned above.
In accordance with this structure, when the driver steps on the accelerator pedal, an accelerator rotor is rotated on the basis of a support shaft together with a pedal arm, and a sensor rotor is rotated together with the accelerator rotor.
Further, on the basis of a change in an angle of rotation of the sensor rotor, a position of a contact portion which is in contact with a resistor applied to a substrate is displaced and an output voltage is increased or decreased, and an opening degree of the accelerator pedal can be detected by detecting the voltage.
The conventional accelerator opening degree detecting apparatus mentioned above is structured such that the driver steps on the accelerator pedal arranged in a leading end of the pedal arm rotatably supported by the support shaft by his or her foot so as to oscillate the pedal arm, and is used as an accelerator opening degree detecting apparatus for a motor vehicle.
On the other hand, in an operation of an accelerator in the two-wheeled vehicle, an accelerator grip is arranged in an end portion of a steering handle, the driver grips the accelerator grip, and the operation of the accelerator is executed by forward and backward rotating the accelerator grip.
In accordance with the structure mentioned above, the pedal arm type accelerator opening degree detecting apparatus for a motor vehicle can not be utilized for the accelerator grip type accelerator opening degree detecting apparatus for a two-wheeled vehicle.
In this case, it can be considered to arrange the accelerator opening degree sensor near the accelerator grip, for example, in a base portion close to the steering handle in the accelerator grip, as the accelerator opening degree detecting apparatus for the two-wheeled vehicle. However, in accordance with the layout of the accelerator opening degree sensor mentioned above, a problem peculiar to the two-wheeled vehicle is generated.
Since the steering handle portion including the accelerator grip of the two-wheeled vehicle is directly exposed to the external, and is arranged so as to protrude to an outermost side, the steering handle portion is damaged at a high probability which is almost necessarily, at a time when the two-wheeled vehicle takes a fall. Accordingly, the accelerator opening degree sensor arranged near the accelerator grip tends to be damaged.
Further, it can be considered to arrange a protection member around the accelerator opening degree sensor, however, the protection member is not preferable because of an increase of the number of parts and in view of an outer appearance of the vehicle body.
Further, since the accelerator grip is directly exposed to the external without being covered by any member, high waterproofness and high weather resistance are required in the accelerator opening degree sensor.